Spinal muscular atrophy

Neuromuscular

Signs and symptoms

The following gives an overview of the signs and symptoms of the different ‘types’ of SMA. It is important to notice that with treatment becoming available for the different types of SMA, the natural course of the different types of SMA is likely to change. Signs and symptoms, as well as severity and rate of progression of the condition, might be different for patients who receive treatment and are likely to depend on the time when treatment is commenced. There is also the possibility that the prolonged survival of patients with the early-onset forms might also lead affected patients to develop new symptoms with age which are currently unknown.


SMA Type 0

This is the most severe form of SMA, also called prenatal SMA as it affects babies during pregnancy. Babies can die before birth, and it is usually fatal within the first few months of life.


SMA Type 1

Babies born with SMA Type 1 show signs of the disease before they are six months old. Without treatment, life expectancy is usually below two years.

 The main symptoms are:

  • Floppiness (low muscle tone)
  • Limited arm and leg movements
  • Unable to sit without support
  • Progressive muscle weakness affecting leg muscles and arm muscles
  • Feeding difficulties due to weak swallowing muscles
  • Breathing difficulties due to weak breathing muscles
  • Weak lungs
  • Weak cry

SMA Type 2

Children born with SMA Type 2 usually show symptoms of muscle weakness between seven and eighteen months of age. Unlike children with Type 1, they reach the ability to sit unsupported and some may achieve the ability to stand with an aid (e.g. standing frame, tilt table). They will not gain the ability to walk unaided and will use a wheelchair and/or electric-powered indoor/outdoor wheelchairs (EPIOCS) for mobility. Some individuals with SMA Type 2 reach adulthood and regardless of their physical disability are able to work and have children.

 The main symptoms are:

  • Floppiness (low muscle tone)
  • Reduced arm and leg movements
  • Unable to walk without support
  • Progressive muscle weakness affecting leg muscles and arm muscles
  • Feeding difficulties due to weak swallowing muscles
  • Breathing difficulties due to weak breathing muscles
  • Weak lungs
  • Scoliosis

SMA Type 3

Individuals diagnosed with SMA Type 3 usually show symptoms in their childhood but in some cases even later, in early adulthood. They reach the ability to walk unaided, although they might lose this ability with the progression of muscle weakness. The severity of symptoms varies significantly from one person to another in SMA type 3, but patients reach adulthood and generally have a normal life expectancy.

The main symptoms are:

  • Progressive muscle weakness in legs and arms
  • Scoliosis
  • Breathing difficulties due to weak breathing muscles causing an increased risk of chest infection
  • They might experience swallowing difficulties but these are much less severe compared to symptoms in patients with SMA type 1 or type 2

SMA Type 4

SMA Type 4 is rare and typically affects adults, with symptoms occurring at any time in their life. The severity of symptoms varies from one person to another but usually, symptoms remain milder than in the other forms. Life expectancy is not affected. i

The main symptoms are:

  • Slowly progressive muscle weakness in legs more than arms
  • Do not usually have breathing and swallowing symptoms as these muscles are not usually affected

 

Link to page 13 of the Guide to the 2017 International Standards of Care for SMA

Last modified
18 December 2019